1. Field
An example of the present invention relates to an illumination optical apparatus, an exposure apparatus, and a device manufacturing method and, particularly, to an illumination optical apparatus suitably applicable to exposure apparatus for manufacturing devices such as semiconductor devices, image pickup devices, liquid-crystal display devices, and thin-film magnetic heads by lithography.
2. Description of the Related Art
The photolithography step for manufacturing the semiconductor devices and others is carried out using an exposure apparatus for projecting a pattern image of a mask (or reticle) through a projection optical system onto a photosensitive substrate (wafer or glass plate coated with a photoresist, or the like) to effect exposure thereof. The ordinary exposure apparatus forms a type of pattern in one shot area (unit exposure region) on the photosensitive substrate.
In contrast to it, Japanese Patent Application Laid-open No. 2000-21748 proposes a double exposure method of doubly printing two types of patterns in one shot area on the photosensitive substrate to form a synthetic pattern.